Project Summary/Abstract Diabetic impairment of angiogenesis complicates peripheral arterial disease (PAD), a painful disorder caused by atherosclerosis in the arteries that reduces blood flow to the lower extremities. Epigenetic mechanisms (e.g., DNA methylation, chromatin modifications and conformational change, and long non-coding RNAs) are implicated in sustained diabetic complications. However, whether and how these conditions influence the epigenetic state of the vascular endothelium and, in turn, cause a chronic impairment in angiogenic function of endothelial cells (ECs) remains largely unknown. We previously identified an enhancer-associated lncRNA that regulates endothelial nitric oxide synthase (eNOS), which we named ?lncRNA that enhances eNOS expression? (LEENE). Our preliminary findings support a novel and essential role for LEENE in the regulation of angiogenesis. Under diabetic conditions, LEENE is suppressed in the ECs of mice and humans; and restoration of LEENE rescues high glucose (HG)-impaired angiogenesis. Mechanistically, LEENE promotes the chromatin accessibility, histone modification, and transcription factor binding at the promoter regions driving angiogenic gene expression. We have also generated a mouse model with genetic deletion of leene, which enables us to test the importance of leene in vascular function, particularly in the context of diabetes- associated PAD. Our central hypothesis is that LEENE promotes physiological angiogenesis, and that suppression of LEENE in diabetes (via HG), impairs angiogenesis, thus contributing to vascular complications such as PAD. To test this hypothesis, we propose three Aims. In Aim 1, we will elucidate the molecular mechanisms by which LEENE promotes angiogenic gene expression under physiological conditions. In Aim 2, we will define the mechanisms by which HG suppresses LEENE to impair angiogenesis. In Aim 3, we will determine the functional importance of LEENE in diabetes-associated PAD in vivo. Collectively, our study will apply innovative approaches to delineate this previously unexplored mechanism underlying angiogenesis and provide novel insights into how angiogenesis is impaired in diabetes to contribute to vascular complications. We expect our results to have far-reaching clinical and therapeutic implications for cardiovascular diseases involving aberrant angiogenesis.